Miscarriage Overview

A miscarriage (also termed spontaneous abortion) is any pregnancy that spontaneously ends before the fetus can survive. Any vaginal bleeding, other than spotting, during early pregnancy is considered a threatened miscarriage. Vaginal bleeding is very common in early pregnancy. About one out of every four pregnant women has some bleeding during the first few months. About half of these women stop bleeding and complete a normal pregnancy.

Threatened miscarriage - Vaginal bleeding during early pregnancy. The bleeding and pain with threatened miscarriage are usually mild and the cervical os (the mouth of the womb) is closed. A health care professional will be able to determine if the cervical os is open upon performing a pelvic exam. Typically, no tissue is passed from the womb. The womb and Fallopian tubes may be tender.

Inevitable miscarriage - Vaginal bleeding along with opening of the cervical os. In this situation, vaginal bleeding is present, and the mouth of the womb is open (dilated). Bleeding is usually more severe, and abdominal pain and cramping often occur.

Incomplete miscarriage - Expulsion of some, but not all, of the products of conception before the 20th week of pregnancy. With incomplete miscarriage, the bleeding is heavier, and abdominal pain is almost always present. The mouth of the womb is open, and the pregnancy is being expelled. Ultrasound would show some material still remaining in the womb.

Complete miscarriage - Expulsion of all products of conception from the womb including fetus and placental tissues. Complete miscarriage is just as it sounds. Bleeding, abdominal pain, and the passing of tissue have all occurred, but the bleeding and pain have usually stopped. If the fetus can be seen, you have miscarried. Ultrasound shows an empty womb.

A miscarriage occurs when a pregnancy ends without obvious cause before the fetus is capable of survival, typically corresponding to the twentieth to 22nd week. This time is measured from the first day of the woman's last menstrual period. Miscarriage is a common complication of pregnancy. It can occur in up to 20% of all recognized pregnancies. This ending of pregnancy is called a spontaneous abortion. In the medical field, the term abortion is often used to describe a miscarriage.

Miscarriage Causes

Miscarriage is caused by the separation of the fetus and placenta from the uterine wall. Although the actual cause of the miscarriage is frequently unclear, the most common reasons include the following:

An abnormal fetus causes almost all miscarriages during the first three months of pregnancy (first trimester). Problems in the genes are responsible for an abnormal fetus and are found in more than half of miscarried fetuses. The risk of defective genes increases with the woman's age, especially if she is older than 35 years.

Miscarriage during the fourth through sixth months of pregnancy (second trimester) is usually related to an abnormality in the mother rather than in the fetus.

Acute infections, including German measles, CMV (cytomegalovirus), mycoplasma ("walking" pneumonia) and other unusual germs can also cause miscarriage.

Diseases and abnormalities of the internal female organs can also cause miscarriage. Some examples are an abnormal womb, fibroids, poor muscle tone in the mouth of the womb, abnormal growth of the placenta (also called the afterbirth), and being pregnant with multiples.

Other factors, especially certain drugs, including alcohol, tobacco, and cocaine, may be related to miscarriage.